Visual shape processing is an essential function that underlies our ability to identify familiar items, interpret facial expressions, and understand written language. Understanding the neural mechanisms behind shape processing would constitute a key insight into visual perception. Previous studies have shown that shape is represented at the earliest of visual cortex (V1 and V2) in terms of oriented edges, and that cells at the highest levels (CIT and AIT) are selective for complex stimuli like hands and faces. Little is known about the intervening stages in which information about oriented edges is transformed into selectivity for complex objects. The long term objectives of this proposal is to fill this gap by investigating the neural mechanisms of shape processing that lead from oriented edges to complex objects pathway (V4,PIT and CIT). The basic strategy of these experiments is to present large sets of stimuli in which shape varies gradually in a systematic fashion, in order to measure shape tuning (in the way that tuning for dimensions like orientation and color has been measured previously. Three basic stimulus sets of increasing shape complexity will be employed. These three stimulus sets correspond to the three specific aims of this project: 1. To determine whether the visual system extracts simple contour features (angles and curve segments) as elementary components of shape. 2. To discover how the visual system represents pairwise combinations of contour features (for example, two right angles conjoined to form one end of a rectangle). 3. To discover how the visual system represents combinations of contour features that close together to form continuous boundaries (for example, three angles conjoined to form a triangle).